The TRH test during dopamine receptor blockade in depressed patients

In an evaluation of the possible role of dopamine on TRH test results, 21 depressed patients were given TRH before and after one week of treatment with a low dose of haloperidol. Haloperidol significantly increased serum prolactin (both basal and after TRH) and cortisol levels, decreased body temperature, and had no effect on serum TSH, growth hormone, or thyroid hormone levels. Five of six patients with initial TSH blunting were retested with TRH; in four patients the TSH response remained blunted. These data render it unlikely that dopamine exerts a major inhibitory input on TSH secretion in depression.